<!DOCTYPE html>
<html lang="en">

<head>
<meta charset="UTF-8">
 <meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
 <title>Document</title>
<script src="../vue.js"></script>
</head>

<body>
<div id="app">

<input type="text" v-model.number.lazy="score">
<div>
    <p v-if="score>90">成绩是A</p>
    <p v-else-if="score>70">成绩是B</p>
    <p v-else-if="score>50">成绩是C</p>
    <p v-else>成绩是D</p>
</div>
</div>
<script>
    Vue.config.productionTip=false;
    const vm=new Vue({
        el:"#app",
        data() {
            return {
                score:null
            }
        }
    })

</script>
 
</body>

</html>